Net Capital Requirements and Customer Protection Requirements (Details) (USD $)	Mar. 31, 2012
Net Capital Requirements and Customer Protection Requirements
Minimum net capital required	$ 100,000
MarketAxess Corporation [Member]
Net Capital Requirements and Customer Protection Requirements
Net capital	62,641,000
Minimum net capital required	1,636,000
Excess net capital	61,005,000
MarketAxess Europe Limited [Member]
Net Capital Requirements and Customer Protection Requirements
Net capital	28,967,000
Minimum net capital required	3,276,000
Excess net capital	25,691,000
MarketAxess Canada Limited [Member]
Net Capital Requirements and Customer Protection Requirements
Net capital	414,000
Minimum net capital required	276,000
Excess net capital	$ 138,000